High-throughput pseudo-binary diffusion couple approach for alloy design in cobalt-based superalloys

Abstract

The paper describes a high-throughput method for alloy design in in Co-based superalloy. The approach is an extension of the diffusion couple method used for the determination of diffusion coefficients. We present the use of such a method in low-density cobalt-based superalloys Co-30Ni-10Al-5Mo-2Ta-2Ti-xCr (x = 0–14 at. %) exploring the effect of Cr content on the microstructural evolution, mechanical, and oxidation properties. The composition profile is developed at relatively high temperature with Co-30Ni-10Al-5Mo-2Ta-2Ti and Co-30Ni-10Al-5Mo-2Ta-2Ti-14Cr as end members in which only the solid solution γ phase grows in the interdiffusion zone. This is subsequently subjected to heat treatment for the evolution of g and γ՛ phases. The composition-dependent microstructure and respective mechanical properties were probed using FE-SEM and nano-indentation respectively. The following composition-dependent properties were successfully probed from the high-throughput diffusion couple: 1) The morphological transition of γ՛ precipitates, 2) The solubility limit of Cr in the alloy for TCP formation, 3) Hardness and average elastic modulus, and 4) The nature and topology of oxidized layers as a function of chromium concentration. Therefore, this method facilitates the optimization of multiple properties in a single experiment, identifying the optimal composition range typically between 5 and 8 at. % of Cr in the present alloy.